Compensator for brush-resistance voltage drop in motor-control systems



Dec. 2, 1930. H, SUNDHAUSSEN 1,783,527

COMPENSATOR FOR BRUSH RESISTANCE VOLTAGE DROP IN MOTOR CONTROL SYSTEMS Filed April 5, 1928 B4 L2 52 B2 INVENTB P Erma/2n, Sand/mussel? etc like.

Patented Dec; 2, 1930 UNITED STATES PATENT OFFICE EERMANllI SUNDHAUSSEH, OF DUSBELDOBI-BATH, GERMANY, ASSIGNOB '10 BKEI- NISGHE-IETALLWALBEN- UND HASCHINENI'AIBBIK, OF DUSSELDOBF-DERENDOBF,

GERMANY GOMPENSATOB FOB BRUSH-RESISTANCE VOLTAGE DROP IN. MOIdR-GONTROL SYSTEMS Application filed April 5, 1928, Serial No.

The invention relates to a connection adapted to keep constant the minimum number of revolutions of a continuous current motor operating according to the Ward Leonard sys- When a continuous current motor is loaded with a determined turning moment, its armatur'e, in order to rotate, must be put at least under that voltage which corresponds to the product of the armature resistance and the required strength of current, disregarding the losses of voltage in the supply wires and the If e. g. the required current load for a determined turning moment is 100 a. and the resistance of the armature winding is 0.1 ohm, then the minimum voltage at which the armature is capable of being rotated is 100.0.1=1O v. With this amount of voltage the motor runs at the minimum number of revolutions at which it can rotate with the given current load. Should the required current strength vary even in the slightest degree, the number of revolutions of the armature will vary, that is, when the required strength exceeds 100 a., the armature stops at once, unless at the same time the voltage supplied is increased in correspondence with the increased loss of voltage in the supply wires and the like. The loss of voltage in the supply wires is proportional to the product of the strength of current and the resistance of these wires; the resistance is to be regarded as constant, if the heating'is neglected.

A constantly varying and absolutely uncontrollable resistance, however, is to be found in the brush contact resistance, which varies constantly according to the specific current load, to the contact pressure of the brushes, the number of revolutions and mode of running of the commutators and to the nature of their contact surface, to the quality and hardness of the brushes and, finally, to the conditions of commutation.

My invention has for its object to so regulate automatically the voltage supplied to the motor in accordance with the degree of brush contact resistance prevailing at any instant, that the motor runs at its minimum number of revolutions without stopping upon 267,534, and in Germany April 12, 1927.

variation in the load. According to the invention this object is obtained with the aid of auxiliary brushes provided on the termi ings each interposed between like terminals of the motor and of the generator.

4 A wiring diagram illustrating the arrangement forming the subject-matter of my invention is. shown in the drawing which accompanies and forms part of this specification.

On each terminal of the generator G and motor M is arranged an auxiliary brush 6,, b b b insulated from the main brushes B B B B ,'the auxiliary brushes of equal polarity being connected with the ends of one of two exciting windings m and n of the generator G, while brushes of unlike polarity are connected with different exciting windings, said windings forming part of auxiliary regulating circuits 2', and 2' respectively which are interposed between'like terminals of the motor and of the generator. The current flowing in the circuit 2' and 2' re-' spectively, of the auxiliary brushes 6,, b and b Z7 respectively is roportional to the drop of voltage between t at commutator segment of the generator and of the motor with which the main brushes are in contact at that particular instant of operation. The resistance of this circuit is composed of the resistance of the supply wire Z and Z respectively, and of the contact resistance of the main brushes B B and 13 ,13 respectively. The'strength of the current flowing in the auxiliary regulating circuits i and 2' is independent of the terminal voltage of the generator G. Therefore the exciting windings n n act correctly at any speed of the motor, that is, on the entire regulating range of the motor as well as also with reversed direction of rotation of the latter, that is, they increase the voltage by permanently exciting additionally the generator in the direction of the separate exciting winding N. When the load increases, then the strength of the current flowing in the ci'rcuitsz' and i increases too and therewith the excitation of the generator and consequently the voltage supplied to the motor by the generator increases proportionally to theloss of voltage arising in the entire clrcuit', this loss being compensated for in this way if the windings m and n are suitably dimensioned. .The speed of the motor is thus kept practically constant, as long as the characteristic of the generator runs rectilinearly.

Instead of the regulating exciting windings n n controlling means, as relays, contact amperemeters and the like may be inserted in the circuit of the auxiliary brushes,

which means in their turn regulate special compensating windings or the separate exciting winding N of the generator G.

What I claim, is

1. In an electric plant a generator and a continuous current motor adapted to be driven by it according to the Ward Leonard system, auxiliar regulating circuits between the terminals 0 said generator and said motor, said circuits including auxiliary brushes on the commutators of said generator and said motor, the brushes of like polarity being connected to the same auxiliary regulating circuit while brushes of opposite polarity are connected with different auxiliary regulating circuits, and means included in said auxiliary circuits for regulating the voltage supplied to said motor in accordance with the varying brush contact resistances of both the said motor and said generator.

2. In an electric plant a generator and a continuous current motor adapted to be driven by it according to the Ward Leonard system, auxiliary regulating circuits between the terminals of said generator and said motor, an exciting winding in each of said regulating circuits, and auxiliary brushes included in said regulating circuits and engaging the commutators of said generator and said motor respectively, the brushes of like polarity being connected to the ends of the same exciting winding, while brushes of unlike polarity are connected with difierent exciting windings.

In testimony whereof I have aflixed my signature.

HERMANN SUNDHAUSSEN. 

